Convergence deflection system for a color picture tube



May 19, 1970 AKIO OHGOSHI ETAL 3,513,350

CONVERGENCE DEFLEGTION SYSTEM FOR A COLOR PICTURE TUBE 2 Sheets-Sheet 1 Filed April 4, 1968 m 0/0 WWW Wm mm OZM 2/ m;

A IPA/5' May 19, 1970 AKIO OHGOSHI ETAL 3,513,350

CONVERGENCE DEFLECTION SYSTEM FOR A COLOR PICTURE TUBE 2 Sheets-Sheet 2 Filed April 4, 1968 36? Q s u INVEN'IORS Ax/o O/vaosw Reva ksm eQ \BQY Q Q NO/Pu Noe/0 Jim- 7/.

United States Patent Office 3,513,350 Patented May 19, 1970 3,513,350 CONVERGENCE DEFLECTION SYSTEM FOR A COLOR PICTURE TUBE Akio Ohgoshi and Minoru Morio, Tokyo, Japan, as-

signors to Sony Corporation, Tokyo, Japan, a corporation of Japan Filed Apr. 4, 1968, Ser. No. 718,730

Claims priority, application Japan, Apr. 6, 1967, 42/22,175; Apr. 6, 1967, 42/29,178 Int. Cl. H01j 29/50, 29/70 US. Cl. 315-13 12 Claims ABSTRACT OF THE DISCLOSURE This invention relates to an electron beam deflection voltage generation means for a color picture tube system and, more particularly, to such deflection voltage generation means for use in color picture tube systems of the single-gun, plural-beam type.

Single-gun, plural-beam type color picture tube systems are known in which the plural electron beams are focussed to converge at a common spot corresponding to a color picture element on the color phosphor screen. In such system utilizing three electron beams, the latter are emitted by suitable beam generating source means and are passed through the optical center of the main focussing lens of the single electron gun with one of the said beams emerging therefrom along the said optical axis and the other of said beams diverging therefrom in opposite directions. Subsequently, the beams are passed through electron beam deflection means located between the said electron gun means and the color screen, wherein the divergent beams are deflected to converge with the cental beam at a common spot in a screen grid, which corresponds to a color picture tube element, and diverge therefrom to properly strike a color picture tube element. In such systems, the three electron beams will be substantially free from the influence of coma and/ or astigmatism of the electron gun main lens due to the passage thereof through the optical center of the said lens. Accordingly, glowing of the beam spots on the color phosphor screen is substantially prevented. In such color picture tube systems it is, however, desirable to provide for both a static electron beam convergence effect and a dynamic hori zontal electron beam convergence effect in order to insure properelectron beam convergence and a resultant, substantially distortionless color picture. Even with the provision of both the static and dynamic convergence effects as discussed above, a problem may arise in the operation of such color picture tube systems in that variations in the anode voltage applied to the picture tube can tend to upset the requisite electron beam convergence at the said common spot to result in turn in degradation of the color picture resolution.

It is, accordingly, an object of this invention to provide electron beam deflection voltage generation means, for use in color picture tube systems of the single-gun, pluralbeam type, which include means to generate both a static electron beam deflection voltage and a horizontal dynamic electron beam deflection voltage and which function to simultaneously apply said static and horizontal dynamic deflection voltages to the system electron beam deflection means.

Another object of this invention is the provision of electron beam deflection voltage generating means as above which are of simplified construction and are cooperatively associated with the system anode voltage generating means in such manner that variations in the anode voltage applied to the color picture tube will have substantially no effect upon electron beam convergence.

Another object of this invention is to provide improved insulator housing means for said electron beam deflection voltage generating means.

In accordance with an aspect of this invention, a simplified convergence deflecting voltage generating circuit is provided which is capable of simultaneously providing both static and horizontal dynamic convergence voltages to the electron beam deflecting means. In one embodiment of the invention, the convergence deflecting voltage generating circuit is cooperatively associated with the color picture tube anode voltage generating means to establish a follow-up relationship between the static convergence deflecting voltage and the anode voltage, whereby variation of the latter will be accompanied by corresponding variation of the former to prevent change in the static convergence condition of the three electron beams and attendant color picture quality degradation. In addition, improved, insulator housing means are provided for the convergence deflecting voltage generating circuit and the said housing means will enable the convenient mounting of the latter from a color picture tube system component and will prevent accidental, convergence deflecting voltage circuit discharge to adjacent system components.

The above and other objects and advantages of this invention are believed made clear by the following detailed description thereof taken in conjunction with the accompanying drawings wherein:

FIG. 1 is a schematic circuit diagram of a color picture tube system of the single-gun, plural-beam type incorporating therein electron beam convergence deflection voltage generation means constructed in accordance with a first embodiment of this invention;

FIG. 2 is a schematic circuit diagram of a color picture tube system of the type of FIG. 1 incorporating therein electron beam convergence deflecting voltage generation means constructed in accordance with a second embodiment of this invention;

FIG. 3 is a top plan view of a housing for supporting and insulating the convergence deflecting voltage generation means of FIGS. 1 and 2; and

FIG. 4 is a cross-sectional view taken along line 4-4 in FIG. 3.

In FIG. 1, a single-gun, three-beam color picture tube system of the chromatron type is indicated generally at A and, briefly described, comprises an electron gun A having cathodes K K and K each of which is constituted by a beam-generating source with the respective beamgenerating surfaces thereof disposed as shown in a plane which is substantially perpendicular to the axis of the electron gun A. A first grid G is spaced from the respective cathodes K K and K and includes apertures g 3 and g formed therein as shown in alignment with the respective cathode beam-generating surfaces. A common grid G is spaced from the first grid G and, in the manner of the former, includes apertures g g and g formed therein in alignment with the respective apertures of the first grid G Successively arranged as shown in the direction away from the common grid G are open-ended, tubular grids or electrodes G G and G respectively, with the respective cathodes K K and K the grids G and G and the electrodes G G and G being maintained in the depicted, assembled positions thereof, by suitable, non-illustrated support means of an insulating material.

For operation of the electron gun A of FIG. 1, appro priate voltages are applied to the grids G and G and to the electrodes G G and G Thus, for example, a voltage of to minus 400 v. is applied to the grid G a voltage of 0 to 500 v. is applied to the grid G a voltage of 13 to 20 kv. is applied to the electrodes G and G and a voltage of O to 400 v. is applied to the electrode G with all of these voltages being based upon the use of the cathode voltage as a reference. As a result, the voltage distributions between the respective electrodes and cathodes, and the respective lengths and diameters thereof, will be substantially identical with those of a unipotential-single beam type electron gun which is constituted by a single cathode and first and second, single-apertured grids.

With the applied voltage distribution as described hereinabove, an electron lens field will be established between grid G and the electrode G to form an auxiliary lens L as indicated in dashed lines, and an electron lens field will be established around the axis of electrode G by the electrodes G G and G to form a main lens L, again as indicated in dashed lines. For a typical use of the electron gun A, bias voltages of 100 v., 0 v., 300 v., kv., 200 v. and 20 v. would be applied respectively to the cathodes K K and K the first and second grids G and G and the electrodes G G and G Further included in the electron gun A of FIG. 1 are electron beam deflecting means F which comprise shielding plates P and P disposed in the depicted spaced, opposed relationship, and axially extending, deflector plates Q and Q which are disposed as shown in spaced, opposed relationship with the outer surfaces of the shielding plates P and P. Although depicted as substantially straight, it is to be understood that the deflector plates Q and Q may, alternatively, be somewhat curved out, as is well known in the art.

The shielding plates P and P and the deflector plates Q and Q are respectively charged and disposed so that the center electron beam B will pass substantially undefiected between the shielding plates P and P, while the respective electron beams B and B will be convergently deflected as shown by the respective passages thereof between the plates P and Q, and P and Q. More spe cifically, a voltage V which is equal to the voltage applied to the electrode G is applied to the respective shielding plates P and P, and a voltage V which is some 200 to 300 v. lower than the voltage V is applied to the respective deflector plates Q and Q to result in the respective shield plates P and P being at the same potential, and to result in the application of a deflecting voltage difference or convergence deflecting voltage V between the respective plates P and Q and P and Q and it is, of

course, this convergence deflecting voltage V which will impart the requisite convergent deflection to the respec tive electron beams B and B In operation, the respective electron beams B B and B which emanate from the beam generating surfaces of the cathodes K K and K will pass through the respec tive grid apertures g g and g to be intensity modulated with what may be termed the red, green and blue intensity modulation signals applied between the said cathodes and the first grid G The respective electron beams will then pass through the common auxiliary lens L to cross each other at the center of the main lens L. Thereafter, the center electron beam B will pass substantially undefiected between the shielding plates P and P since the same are at the same potential. Passage of the electron beam B between the plates P and Q and of the electron beam B between the plates P and Q will, however, result in the convergent deflections thereof as a result of the convergence deflecting voltage V applied therebetween, and the system of FIG. 1 is so arranged that the electron beams B B and B will subsequently converge or cross each other at a common spot between adjacent grid wire g of the beam landing position determining grid or mask G and will diverge therefrom to strike the color phosphor screen S. More specifically, it may be noted that the color phosphor screen S is composed of a large plurality of sets of vertically extending red, green and blue phosphor stripes S S and S with each of the said phosphor stripe sets forming a color picture element as in a chromatron type color picture tube. Thus may be understood whereby the common spot of beam convergence will correspond to one of the thusly formed color picture elements.

The voltage V is also applied to the screen S as an anode voltage in conventional manner through a nonillustrated graphite layer which is provided on the inner surface of the non-illustrated cathode ray tube cone por tion to which is also coupled the electrode G The screen grid G comprises one grid wire g for each phosphor stripe set of the screen S, and a post-focussing voltage V ranging, for example, from 6 to 7 kv. is applied as indicated to the said screen grid. Thus, to summarize the operation of the depicted color picture tube system of FIG. 1, the respective electron beams B B and E will be converged at the screen grid G and will diverge therefrom in such manner that the electron beam B will strike the blue phosphor stripe S the electron beam B will strike the green phosphor stripe S and the electron beam B will strike the red phosphor stripe S Non-illustrated horizontal and vertical beam deflecting means are, of course, provided to effect electron beam scanning of the face of the color phosphor screen in conventional manner, whereby a color picture will be provided thereon. Since, with this arrangement, the respective electron beams are each passed, for focussing, through the center of the main lens L of the electron gun A, the respective beam spotsformed by the respective electron beam impingements on the color phosphor screen S will be substantially free from the effects of coma and/or astigmatism of the said main lens, whereby improved color picture resolution will be provided.

A convergence deflecting voltage generating circuit constructed in accordance with a first embodiment of this invention is indicated generally at 25 and is connected as indicated to the electron gun means A to provide the requisite static convergence deflecting voltage to the latter. The convergence deflecting voltage generating circult is also connected to a fly-back transformer as generally indicated at 21 which is in turn connected to the non-illustrated, conventional horizontal deflection voltage output circuit of the color picture tube system of FIG. 1. The fly-back transformer 21 comprises a closed magnetic core 22 and a high voltage winding 23 wound therearound as shown. Also wound on the magnetic core 22 is a convergence deflecting voltage winding 24 which functions as a circuit element in the convergence voltage deflecting generating circuit 25. More specifically, the convergence deflecting voltage generating circuit 25 comprises series-connected diode 26 and resistors 27 and 28 which are in turn connected as indicated across the |winding 24 with the diode 26 being connected in the forward direction. In addition, series-connected capacitors 29 and 30 are connected in parallel with the resistor 28, and an inductor 31 is connected as shown between the anode side of the diode 26 and the connection point of the respective capacitors 29 and 30. Circuit terminals 32a and 32b are connected across the resistor 28.

In operation, the voltage developed in the winding 24 is rectified by the rectifier circuit formed by the diode 26, resistors 27 and 28, and capacitors 29 and 30 to provide a static convergence deflecting voltage V across the resistor 28 and thus between the terminals 32a and 32b with the potential of the former being higher than that of the latter. In addition, the voltage developed across the winding 24 is converted into a voltage of parabolic wave form by means of the connected inductor 31 and capacitor 30 which, as utilized herein, will function in the nature of a double-integrating circuit. This voltage of. parabolic wave form is provided as a horizontal dynamic convergence voltage V' which is also available, through capacitor 29, between the respective circuit terminals 32a and 32!). As a result, the respective static and dynamic convergence voltages V and V' are superimposed upon each other to result in the provision of a voltage (V V between the circuit terminals 32a and 32b.

Referring again to the fly-back transformer 21 it may be noted that the high voltage winding 23 thereof is coupled to the anode of a high voltage rectifier diode 33,

the cathode or DC. side of which is connected to the terminal 325 of the circuit 25. A terminal 34 is provided for the spaced, deflecting plates Q and Q and is connected as shown to the terminal 321), and a terminal 35, commonly referred to as the anode button, is tied to each of the electrodes G and G and the shielding plates P and P, and is connected as shown to the terminal 32a of the circuit 25. The terminal 35 is also connected with the non-illustrated, cathode ray tube cone portion graphite layer discussed hereinabove. As a result, the voltage appearing at the terminal 35 will be applied to each of the electrodes G and G the shielding plates P and P, and as an anode voltage to the color phosphor screen S, with the dashed capacitor C denoting an equivalent capacitance which exists between the terminal 35 and ground.

With a convergence deflecting voltage generating circuit as described, a voltage V appearing at the DC. output side of the rectifier diode 33, and thus at terminal 34, will be applied to the deflecting plates Q and Q, and the anode voltage V which is equal to (V -l- V -l-V will appear at circuit terminal 32a, and thus terminal 35, and will be applied to the electrodes G and G the shielding plates P and P, and the color phosphor screen S. As a result, the static convergence deflecting voltage V which is equal to (V V will be applied between the plates P and Q and between the plates P and Q with, in this instance, the potential at the plates Q and Q being negative with respect to that at the plates P and P. In addition, the dynamic convergence deflecting voltage V which is provided between the circuit terminals 32a and 3212, will be superimposed upon the static convergence deflecting voltage V so as to also be applied between the electrode plates P and Q and between the electrode plates P and Q. Thus it is believed made clear whereby the static convergence deflecting voltage V is applied to the convergence deflecting means F of the depicted single-gun, three-beam type color picture tube system to provide for proper convergence of the respective electron beams B B and B at the common spot in the screen grid G the attendant proper striking of the beams on the respective color phosphor stripes S S and S In addition, the dynamic convergence deflecting voltage V will be simultaneously applied to the deflecting means F to result, in combination with the application of the deflecting voltage V in the provision of a substantially distortionless color picture.

In the system of FIG. 1, the part of the anode voltage V which is utilized to effect the static convergence deflecting action on the electron beams is equal to (V V to make clear that the deflection voltage V will of course vary in accordance with variations in the anode voltage V With the system of FIG. 1, however, any variation in this anode voltage V which could result in variation of the convergent condition of the three electron beams B B and B at the common spot in the screen grid G may be readily compensated for. More specifically, and as is well known in this art, it the brightness of a color picture on the color screen is varied, the anode current of the color picture tube varies correspondingly, whereby, in the system of FIG. 1, the anode voltage V at the terminal may be readily understood to vary in accordance with color picture brightness variation.

As disclosed herein, the static convergence deflecting voltage V is available across the series circuit of the capacitors 29 and 30. However, since the anode current flows through the capacitors 29 and 30 in such direction as to effect the discharge thereof, the voltage V will be varied in accordance with variations in the anode voltage V Thus, for example, if the anode voltage V is decreased with an increase in the anode current, the voltage V will also be decreased. In order that the convergent condition of the three electron beams at the common spot in the screen grid G be maintained unchanged, it is required that the ratio V /V be maintained at a substantially constant value. Since in the system of FIG. 1, variation in the anode voltage V will always be accompanied by correspondingly directed change in the voltage V the critical ratio V /Vp will be maintained at a substantially constant value irrespective of the changes in the anode voltage V and this corresponding change or follow-up of the voltage V relative to changes in the anode voltage V can be best achieved by selection of resistors 27 or 28 of proper resistance values. Accordingly, and with proper resistance value selection, it is believed made clear that the color tube system of FIG. 1 will function to maintain proper electron beam convergence at the screen grid G despite anode voltage variations.

A further advantage in the system of FIG. 1 is the fact that the number of turns of the high voltage winding 23 of the fly-back transformer 21 can be reduced by the number of turns required for the generation of the voltage V because the output voltage of the rectifier 33 which is connected to the winding 23, need only be VQ which is equal to (V V In addition, the breakdown voltage requirements of the rectifier diode 33 can be reduced to (V -V as should be obvious.

Although it might be considered that the superimposition of the dynamic convergence deflecting voltage V' upon the anode voltage Vp might give rise to adverse, color tube system operating effects, in practice this is not the case because the dynamic convergence voltage V' has a value of 20 v. or less which may readily be understood to be negligibly small when compared with the anode voltage V which ranges from 13 to 20 kv.

Referring now to the color tube system of FIG. 2, as generally indicated at 7, the same may readily be seen to be very similar to the color tube system 5 of FIG. 1, whereby corresponding reference characters are utilized to identify corresponding system components in each of the said systems. In FIG. 2, a second embodiment of the convergence deflecting voltage generating circuit of the invention is indicated generally at 25 and differs from the convergence deflecting voltage generating circuit 25 of FIG. 1 in that, in the circuit 25, the series connected diode 26 and resistors 27 and 28 are connected as shown across the fly-back transformer winding 24 with the polartiy of the diode 26 being reversed. Thus, and since the output terminals 32a and 32b of the circuit 25' remain coupled respectively to the electron gun terminals 34 and 35, the dynamic convergence deflecting voltage V' available across the output terminals of the circuit 25 will be such that the potential at the circuit terminal 32b is higher than that at the circuit terminal 32a as opposed to the system of FIG. 1.

The output voltage V of the high voltage rectifier diode 33 is however, in the manner of the system of FIG. 1, applied through the terminal 35 as the anode voltage to the plates P and P, the electrodes G and G and again, through the non-illuminated cathode ray tube graphite layer, to the color phosphor screen S, while the voltage VQ which is here equal to is again applied to the plates Q and Q of the deflecting means through the terminal 34. Thus, the static convergence deflecting voltage V will be applied between the plates P and Q and between the plates P and Q, and the dynamic convergence voltage V,;; will be superimposed thereupon to provide the requisite, electron beam convergence effect, all in the manner described hereinabove with regard to the color tube system of FIG. 1. In the convergence deflecting voltage generating circuit of FIG. 2, however, the capacitors 29 and 30 are not in the path of the anode current whereby the follow-up of the convergence deflecting voltage V to variations in the anode voltage V occasioned by variations in the anode current, will not be achieved.

The high voltage nature of the convergence deflecting voltage generating circuits 25 or 25' make possible electrical discharge between the same and other circuits disposed closely and/or connected thereto, which electrical discharge in addition to leading to operational circuit instability could also, of course, become very dangerous. To eliminate this electrical discharge possibility, the convergence deflecting voltage generating circuits 25 or 25' are respectively housed in an insulator casing 41 which is in turn supported from the magnetic core 22 of the fly-back transformer 21 in a manner made clear in FIGS. 3 and 4. More specifically, the insulator casing 41 comprises a pair of casing halves 41a and 41b having outer walls 42a and 42b in surface contact, and cylindrical, surface-contacted members 43a and 43b which form a transformer core mounting aperture 46 and are connected as indicated to the walls 42a and 42b. The winding 24 (FIGS. 1 and 2) is wound on the cylindrical member 43a in the insulator casing half 4101, and there is provided a circuit board 44 on which are mounted as shown the diode 26, resistors 27 and 28, capacitors 29 and 30 and inductor 31.

Before assembly, the circuit elements are mounted and connected as described above, following which the insulator casing half 41b is placed over insulator casing half 41a and secured thereto in any convenient manner, and lead wires 45a and 45]) are extended through apertures provided therefor in the respective walls 42a and 42b to function as the circuit terminals 32a and 32b as described hereinabove. Following this, the magnetic core 22 of the fly-back transformer 21 is inserted as indicated through the insulator casing aperture 46 to effect the mechanical support of the insulator casing from the core as should be obvious.

By such construction, the convergence deflecting voltage generating circuits 25 or 25' may be completely insulated from adjacent tube system elements or adjacent electrical systems to prevent electrical discharge therebetween, and insure operational stability of the said convergence deflecting voltage generating circuits. Thus, the danger of high voltage circuit discharge is removed.

The convergence deflecting voltage generating circuits 25 and 25' are not limited to the specific arrangements thereof depicted in FIGS. 1 and 2, but rather, it is believed apparent that many modifications and changes in the respective circuit elements and/or the respective manners of connection thereof are possible. In like manner, various modifications and changes in the construction of the insu lator casing 41 as depicted in FIGS. 3 and 4, and the manner in which the same is supported from the magnetic core 22 of the fly-back transformer 21 are also possible. Thus it is believed apparent that many modifications and variations, other than those described hereinabove, may be effected in the disclosed embodiments of this invention without departing from the spirit and scope thereof as defined by the appended claims.

What is claimed is:

1. In a color picture tube comprising a color screen, an electron gun means having at least one electrode to which an anode voltage is to be applied and including beam generating means for directing a plurality of electron beams toward said color screen, focussing lens means for focussing said electron beams at said color screen with one of said electron beams emerging from said lens means along the optical axis of the latter and with the other of said beams emerging from the lens means along paths that are divergent with respect to said axis, and wherein horizontal deflecting pulses are supplied to the tube for causing said electron beams to scan said screen; convergence effecting means for deflecting those electron beams which emerge from said lens means along said divergent paths to cause convergence of all of said beams at a common spot corresponding to a color picture element on said screen, said convergence effecting means comprising first and second spaced plates disposed at opposite sides of each of said divergent paths to electrostatically deflect the beam in the respective path when at different potentials, high voltage generating means operable in response to said horizontal deflecting pulses to generate a high voltage as an output therefrom, convergence voltage generating means also operable in response to said horizontal deflecting pulses to generate at least a static convergence deflecting voltage, said voltages being generated by the same source, circuit means connected to the outputs of said voltage generating means to superimpose said high voltage on said static convergence deflecting voltage so that said convergence voltage generating means has an output constituted by the resultant of the superimposed voltages, means applying said output of one of said Voltage generating means to said first plates, means applying said output of the other of said voltage generating means to said second plates whereby to establish the potential difference between said first and second plates for deflecting the respective beam, and means applying the larger of said outputs to said electrode as said anode voltage to be applied thereto.

2. A color picture tube as in claim 1, in which said high voltage is added to said static convergence deflecting voltage in said output from said convergence voltage generating means and said output constituted by the sum of said high voltage and said static convergenc deflecting voltage is the output applied to said electrode as the anode voltage, and said convergence voltage generating means includes circuit means to maintain a substantially constant ratio of said static convergence deflecting voltage to said anode voltage, whereby to ensure maintenance of convergence of said beams at said common spot upon variations in said anode voltage by reason of changes in the anode current of the tube.

3. A color picture tube as in claim 1, in which said circuit means includes means whereby said static convergence deflecting voltage is subtracted from said high voltage to provide the difference therebetween as the voltage at said output from said convergence voltage generating means, and said output of the high voltage generating means is the one applied as anode voltage to said electrode.

4. A color picture tube according to claim 1, in which said convergence voltage generating means further includes means to generate a horizontal dynamic convergence voltage superimposed on said static convergence deflecting voltage so as to be included in said output from the convergence voltage generating means and thereby impart a horizontal dynamic convergence eflect to the plurality of beams converged at said common spot.

5. A color picture tube according to claim 4, in which a fly-back transformer receives said horizontal deflecting pulses, and said convergence voltage generating means includes a coil on said transformer, rectifier circuit means connected with said coil to produce said static convergence deflecting voltage, and integrating circuit means also connected with said coil for producing a parabolic waveform voltage constituting said horizontal dynamic convergence voltage.

6. A color picture tube according to claim 5, in which said convergence voltage generating means is housed in an insulating casing and the latter is mounted on said transformer.

7.A color picture tube according to claim 1, in which a fly-back transfonmer receives said horizontal deflecting pulses, said convergence voltage generating means includes a first coil on said transformer and rectifier circuit means connected with said first coil to produce said static convergence deflecting voltage, and said high voltage generating means includes a second coil on said transformer and rectifier circuit means connected with said second coil to produce said high voltage.

8. A color picture tube according to claim 7, in which said convergence voltage generating means is housed in an insulating casing mounted on said transformer.

9. In a color image reproducing system including a cathode ray tube having a luminescent screen and electron gun means having at least one electrode to which a high voltage anode voltage is applied, said electron gun including beam generating means for directing a plurality of electron beams toward said screen at divergent path angles, convergence appartus for controlling the converg ence of said beams at a common location corresponding to a color picture element on said screen, said convergence appartus comprising first and second spaced plates disposed on opposite sides of said divergent paths to electrostatically deflect the beam when said plates are at different potentials, means for generating a high voltage, means for generating a static convergence deflection voltage V convergence circuit means connected to the output of said voltage generating means to superimpose said static convergence deflection voltage V on said high voltage so that said convergence circuit means has an output constituted by the resultant of said voltages, means applying said high voltage to said first plates, means applying the output of said convergence circuit means to said second plates whereby a potential difference V is established between said first and second plates for deflecting a beam passing therethrough.

10. A color image reproducing system in accordance with claim 9 wherein means are included for generating a dynamic convergence deflection voltage V the output of said dynamic convergence deflection voltage means being connected to said convergence circuit means for superimposing said dynamic convergence deflection voltage V on said static convergence deflection voltage V 11. A color image reproducing system in accordance with claim 10 wherein said static and dynamic convergence deflection voltages are generated by the same source.

12. A color image reproducing system in accordance with claim 9 in which said convergence circuit means includes circuit means for maintaining the ratio between the static convergence deflection voltage and the anode voltage (V V substantially constant whereby convergence of said beams at a common location is ensured regardless of variations in said anode voltage.

References Cited UNITED STATES PATENTS 2,679,614 5/1954 Friend. 2,716,718 8/ 1955 Sonnenfeldt. 2,907,915 10/ 1959 Gleichauf. 2,928,981 3 /1960 Kolesnik et a1. 2,975,325 3/1961 Gundert et a1. 3,163,797 12/ 1964 Singleback.

RODNEY D. BENNETT, Primary Examiner M. F. HUBLER, Assistant Examiner 

